how to limit # of words/post on my main blog page

hi - i can't figure out how to limit the number of words displayed for each post before the reader sees a link to "read more". Is there a way to do this so that my longer posts don't break up the flow too much? thanks, Oliver

There is no means that I know of for automatically limiting the number of words previous to the insertion of a <!--more--> tag. On the Hemingway theme a short excerpt is hardcoded into the theme and cannot be changed. On all other wordpress.com themes the blogger chooses where to insert the more tag.

Opinion:
A word to the wise (if you're willing to listen) is don't overdo the use of the <!--more--> tag by using it in every post. Many bloggers such as myself are loathe to have to click twice on every post to read them. Moreover we find the practice of using the tag to obtain double stats to be offensive enough to simply stop visiting the blogs where this is the set-up.

Setting the number of posts on your front page is done here
-> Options -> Reading
Blog Pages
Show at most: ___posts
(Enter the number of posts you prefer and then click "Update Options" to save.

Using the more tag to break text on long posts
(1) If you are using the visual rich text editor then use icon number 13 where you want the break to occurhttp://faq.wordpress.com/2006/05/15/what-do-all-the-icons-mean/
(2) Of you are using the standard editor use the [more] button where you want the break to occur
(3) If you are hand coding insert <!--more--> where you want the break to occur
(4) If you do not like the text the themes provides you can insert your own <!--more your own text here!-->

the # of posts seems to be set at a default of 10. if i'm writing 1 post/day (e.g. 30/month), is there any reason not to set this to 20 or 30?

The reasons one does not set more than 7 - 8 medium lengths posts on a front page are
(1) page loading time (70% of people on the net are on dial-up service
(2) limiting scrolling - no one wants to scroll down a front page that's miles long and it's likely they will abandon the blog, whereas if you have your Recent Posts widget up in your sidebar the readers may be more inclined to click on and read additional posts that aren't on the front page.

Think of the newspaper test and ask yourself just how long a page would you put up with before you folded it.